Which block cipher modes of operation allow a predictable IV?I'll just note two reasons why your answer is good but not helpful to me. EAX is not available in .NET (at least to my knowledge. CBC,ECB,OFB,CFB,CTS all appear to be). In my situation I dont want to store the random IV anywhere which is why i am asking for ciphers which allow me to use predictable IVs. -edit- i am encrypting certain columns on a per row bases.

Cryptographic GUID?@CodesInChaos: I'm not sure exactly how much i need. A GUID may be allowed. What I do require is not knowing the origins of the machine that created the number. Time may be ok but i prefer not to have it. Maybe a PRNG is fine but how do i seed it? time ^ random_seed.Take(16)